This project is attempting to discover and characterize endogenous inhibitors of bradykinin. It uses the ability of substances to inhibit the first step in bradykinin action, binding to receptors, as a screening device. The putative inhibitors will be extracted from animal tissues. The receptors will be prepared from bovine uterus. The binding reaction will use labeled tyrosine-1-kallidin. Inhibitors will be isolated from lipid extracts by column chromatography. Any fractions showing inhibition will be tested for biological activity in standard bioassays using contractile tissue, such as bovine myometrium. It is hoped that inhibitors of bradykinin will be useful tools in discovering the role this hormone plays in normal and abnormal states involving bronchoconstriction or inflammation. Although it is known that bradykinin is potent in mediating bronchoconstriction and inflammation under experimental conditions, it is not known whether the hormone has any significant role in spontaneous conditions or diseases. In addition to serving as tools for improved understanding of bradykinin's functions, inhibitors may be threapeutic agents if bradykinin is, indeed, an endogenous toxin involved in diseases.